mash: Fix ShelfItem mojo struct; add enums and traits.

ash/public/cpp/shelf_item.h

Index: ash/public/cpp/shelf_item.h
diff --git a/ash/common/shelf/shelf_item_types.h b/ash/public/cpp/shelf_item.h
similarity index 80%
rename from ash/common/shelf/shelf_item_types.h
rename to ash/public/cpp/shelf_item.h
index 62d279eb6bcdbc615f63169ac3a56227293a4c91..56eaad965cd9edce82fefa4748b50b0ab98f9bef 100644
--- a/ash/common/shelf/shelf_item_types.h
+++ b/ash/public/cpp/shelf_item.h
@@ -2,22 +2,20 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef ASH_COMMON_SHELF_SHELF_ITEM_TYPES_H_
-#define ASH_COMMON_SHELF_SHELF_ITEM_TYPES_H_
-
-// TODO(msw): Rename these files to shelf_item.*; audit users.
+#ifndef ASH_PUBLIC_CPP_SHELF_ITEM_H_
+#define ASH_PUBLIC_CPP_SHELF_ITEM_H_
 
 #include <string>
 #include <vector>
 
-#include "ash/ash_export.h"
+#include "ash/public/cpp/ash_public_export.h"
 #include "ash/public/cpp/shelf_types.h"
 #include "base/strings/string16.h"
 #include "ui/gfx/image/image_skia.h"
 
 namespace ash {
 
-struct ASH_EXPORT ShelfItem {
+struct ASH_PUBLIC_EXPORT ShelfItem {
   ShelfItem();
   ShelfItem(const ShelfItem& shelf_item);
   ~ShelfItem();
@@ -50,4 +48,4 @@ typedef std::vector<ShelfItem> ShelfItems;
 
 }  // namespace ash
 
-#endif  // ASH_COMMON_SHELF_SHELF_ITEM_TYPES_H_
+#endif  // ASH_PUBLIC_CPP_SHELF_ITEM_H_